Outbreak caused by a multi-resistant Klebsiella pneumoniae strain of new sequence type ST341 carrying new genetic environments of aac(6')-Ib-cr and qnrS1 genes in a neonatal intensive care unit in Spain

Abstract An outbreak due to a Klebsiella pneumoniae clone occurred in a neonatal intensive care unit of a Spanish Hospital in which three newborns were infected (all with gestational age ≤29 weeks; two of them died) and seven were colonized (gestational age >32 weeks; none died). One K. pneumoniae strain per patient was further characterized. The 10 strains showed an indistinguishable pulsed-field-gel-electrophoresis pattern, were typed in the phylogenetic group KpI and were ascribed into a new sequence type registered as ST341. All 10 strains presented the same multiple-antibiotic-resistant phenotype, showed extended-spectrum-beta-lactamase production, and harbored the bla CTX-M-15 , bla SHV-11 , bla OXA-1, aac (6′)-Ib-cr, qnrS1 , aac (3)-II, aph (3′)-Ia and aadA5 resistance genes. No class 1 or class 2 integrons were detected. The bla CTX-M-15 gene presented the following genetic environment: IS Ecp1-bla CTX-M-15 -orf477. These strains contained two copies of the aac (6′)-Ib-cr gene included in the following new genetic environments: aac (3)-II - IS 26-aac (6′)-Ib-cr -bla OXA-1 and aac (3)-II - IS 26- Δ catB3 - bla OXA-1 -aac (6′)-Ib - cr (registered at GenBank with accession numbers GQ438247 and GQ438248, respectively). The genetic environment of the qnrS1 gene (IS 26 -ΔIS Ecl 2- qnrS1 ) (GenBank accession number GQ438249) was also not described previously. The aac (6′)-Ib-cr, qnrS1 , bla CTX-M-15 , aac (3)-II, and bla OXA-1 genes, located in a plasmid of 33.5 kb, could be transferred to Escherichia coli by transformation.